Ethylene oxide (EO) is a useful reactive compound employed as a starting material in the manufacture of glycols, polyglycols, ethanolamines and polyethanolamines. It is highly flammable even in the absence of oxygen since it can undergo auto-oxidation under the appropriate temperature conditions or spark initiation.
Presently, it is the approved practice to ship EO with a nitrogen pad so that the vapor above it contains not less than 45% nitrogen. In the case of bulk marine shipment, there are additional requirements including cooling facilities to maintain the temperature below 90.degree. F. (32.2.degree. C.), tank construction with respect to pressure and materials and other numerous regulations (see Fed. Reg. Vol. 35, No. 38, Feb. 25, 1970). Because of these regulations the number of ships available is limited, at present there being only two such which are approved by the U.S. Coast Guard for carrying EO.
It would be most advantageous if a method of shipping could be found which would eliminate the need for shipping EO under the above indicated stringent requirements.
One possible solution to the problem of shipping EO would be to convert it to ethylene carbonate and then regenerate at the use-site. This solution is not attractive because the carbonate is 50% CO.sub.2 by weight and the cost of shipping a product half of which is to be discarded would be too great.
It has now been discovered that safe shipment of EO can be accomplished by providing mixtures of EO with propylene oxide (PO) wherein the liquid mixture is of a composition such that the vapor composition contains at least 30% by weight PO. Such mixtures are not flammable in the absence of oxygen, i.e. they will not auto-oxidize. Liquid mixtures of EO and PO which contain up to 48% EO will provide such a non-flammable vapor.